Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$107.80	9.418%	$117.9526	$117.95	$117.95	$118.00
Purchase #2	$62.45	13.116%	$70.6409	$70.64	$70.65	$70.60
Purchase #3	$95.83	12.266%	$107.5845	$107.58	$107.60	$107.60
Purchase #4	$126.97	13.809%	$144.5033	$144.50	$144.50	$144.50
Purchase #5	$130.58	8.664%	$141.8935	$141.89	$141.90	$141.90
Purchase #6	$209.99	13.577%	$238.5003	$238.50	$238.50	$238.50
Purchase #7	$103.41	7.677%	$111.3488	$111.35	$111.35	$111.30
7 purchase totals =	$837.03		$932.4239	$932.41	$932.45	$932.40